Flame retadant polypropylene resin composition

ABSTRACT

The present invention provides a flame retardant resin composition, or more particularly, a flame retardant polypropylene resin composition which comprises polypropylene having improved flow melt characteristics, flame retardants, a flame retardant aid, and a tetrafluoroethylene polymer. The composition of the present invention has high melt tension, without deterioration of the mechanical properties of flame retardant polypropylene, and drastically enhanced characteristics of shape maintenance and a flaming drip during burning.

TECHNICAL FIELD

[0001] The present invention relates to a flame retardant resincomposition, or more particularly, to a flame retardant polypropyleneresin composition which comprises polypropylene having improved flowmelt characteristics, flame retardants, a flame retardant aid, and atetrafluoroethylene polymer. The resin composition of the presentinvention has high melt tension, without deterioration of the mechanicalproperties of flame retardant polypropylene, and drastically enhancedcharacteristics of shape maintenance and flaming drip during burning.

BACKGROUND ART

[0002] As for the conventional resins used in electrical products,non-combustible, flame retardant, or self-extinguishing resins are usedfor the purposes of preventing ignition, combustion or fire, which maybe caused by various electrical troubles therein. In this regard, sinceolefin-based resins made from hydrocarbons(i.e., polypropylene) haveexcellent impactability, rigidity, appearance and moldability, variousproposals have been made relating to flame retardancy of these resins.In particular, according to the standards of flame retardancy ofelectrical products, the UL specifications (UL94) of the US require ahigh level of flame retardancy, depending on the products and the parts.The products to be exported to the US are required to be made frommaterials deemed to be appropriate according to the UL specifications.In response to these requirements, researchers have developed a materialof thermoplastic polyolefin resins, mixed with organic and inorganicflame retardants, and a flame retardant aid. However, the material isproblematic in that it suffers from the occurrence of a flaming drip. Tosolve this problem, a flame retardant resin composition was proposed,wherein said composition comprises 30˜80 wt % of polypropylene; 5˜25% ofpolyethylene having a melt flow rate of 0.01˜2.0 g/10 minutes (190° C.,21.18N); 10˜35 wt % of an inorganic fillers selected from the groupconsisting of powder talc, kaoline, mica, and silica; and 3˜35 wt % ofdecabromodiphenylether and/or dodecachlorodecahydrodimetabibenzocyclocutene (Japanese Patent Publication No. Sho55-30739). In the above patent, it was reported that polyethylene actsin effect to facilitate the melt flow drip therein during burning.However, with respect to the composition as such, if the melt flow rate(MFR, 190° C.; 21.18N) of polyethylene is low, there is a problem ofinsufficiency in even dispersion of polypropylene-based flame retardantresins. For this reason, an increase in melt tension is not seen, withinsubstantial effects on the improvement of the properties of shapemaintenance and a flaming drip. Consequently, if the amount ofpolyethylene in the composition is 5 wt % or less, a proper melt-dripcharacteristic is not obtained. Conversely, if the amount in thecomposition increases, the temperature of thermal deformation, rigidity,etc. deteriorate. Moreover, the superior characteristics ofpolypropylene are lost.

[0003] Moreover, as for the method of increasing melt tension or thetemperature of crystallization of a polypropylene composition, there areseveral methods as follows: a method of reacting organic peroxides andcross-linking agents to crystalline polypropylene in the molten state(Japanese Patent Laid-Open Nos. Sho 58-93711, Sho 61-152754, etc.); anda method of producing polypropylene having free monomer chain brancheswithout gel by reacting semi-crystalline polypropylene with a peroxideof a low decomposition temperature in the absence of oxygen (JapanesePatent Laid-Open No. Pyung 2-298536). In addition, as for the othermethods of enhancing melt visco-elasticity (e.g., melt tension),researcher have proposed a composition of a mixture of polyethylene orpolypropylene of different specific viscosities or molecular weights, ora method of obtaining such a composition by means of multi-steppolymerization. For example, the following methods have been proposed: amethod of extrusion in the temperature range of the melting point to210° C. after adding 2˜30 weight parts of polypropylene of ultra-highmolecular weight to 100 weight parts of commonly-used polypropylene(Japanese Patent Publication No. Sho 61-28694); a method of multi-steppolymerization, yielding an extrusion sheet which comprises twocomponents of polypropylenes of different molecular weights, having alimiting viscosity number ratio of 2 or higher (Japanese PatentPublication No. Pyung 1-12770); a method involving a polymer of 1˜10 wt% of polyethylene of low viscosity; a method of melt-mixing three typesof polyethylenes of different viscosities and molecular weights; amethod of multi-step polymerization of polyethylene of ultra-highmolecular weight having limiting viscosity number of 20 dl/g or higher,wherein less than 0.05˜1 wt % of the polyethylene is obtained(JapanesePatent Publication No. Pyung 5-79683); and a method of multi-steppolymerization of less than 0.05˜1 wt % of polyethylene of ultra-highmolecular weight having limiting viscosity number of 15 dl/g or higherby means of using 1-butene or 4-methyl by way of a polymerizer of aspecific alignment, wherein (Japanese Patent Publication No. Pyung7-8890).

[0004] With respect to the various compositions or the methods ofpreparation thereof as proposed in prior art, those methods enhance melttension of polyolefin to a certain extent. However, there are problemsof inadequacy of recycling usability with those cross-linkedcompositions in addition to the problems of low rigidity at hightemperature. Furthermore, with respect to those using polyethylene ofhigh viscosity, there are many factors which need improvements: e.g., anincrease in electricity consumption due to an increase in current loadat the motor of a molding machine, limitation in productivity, and lowthermal stability. Moreover, with respect to the method of preparingpolyolefin polymers of high molecular weights, according to said methodof multi-step polymerization, it is difficult to control a lowpolymerization level in olefin (co)-polymerization for producing a smallamount of polyolefin of high molecular weight In addition, it requireslow polymerization temperature for producing polyolefin of sufficientlyhigh molecular weight. The method also requires reconstruction of theprocess, which all leads to lowering of productivity of polyolefin.

[0005] In the end, with respect to the prior art as mentioned above, itbrings about insufficient enhancement in terms of melt tension ofpolypropylene and its crystallization temperature. In particular, acomposition having superior rigidity and moldability has not beendeveloped as of yet, which simultaneously satisfies the characteristicsof shape maintenance, and a flaming drip or melt drip at the time ofburning of a flame retardant polypropylene resin composition comprisinga halogen-based flame retardant.

DISCLOSURE OF INVENTION

[0006] In solving these problems as mentioned above, the objective ofthe present invention lies in providing a flame retardant polypropyleneresin composition having improved characteristics of shape maintenanceand a flaming drip.

[0007] The flame retardant polypropylene resin composition of thepresent invention comprises (A) a polypropylene resin having a melt flowrate (hereinafter MFR) of 1.5˜40 g/10 minutes at 230° C. and a 2.16 kgload; (B) at least one of flame retardants and a flame retardant aid;and (C) 0.10˜3 wt % of a tetrafluoroethylene polymer.

[0008] With respect to the flame retardant polypropylene resincomposition of the present invention, the polypropylene resin refers toa propylene α-olefin block copolymer having 50 wt % or more of propylenepolymer units or a propylene homopolymer. In other words, thepolypropylene resin used in the present invention refers to acrystalline polypropylene homopolymer, or a copolymer of propylene andone or more compounds selected from the group consisting of 1-butene,1-pentene, 1-hexene, 4-methylpentene, 1-heptene, 1-octene, and 1-decene.The melt flow rate of the polypropylene resin should be 1.5˜40 g/10minutes, or preferably 2˜40 g/10 minutes. If the melt flow rate is lessthan 1.5 g/10 minutes, the injection molding of a thin product becomesrather difficult, which is not preferable. If the melt flow rate exceeds40 g/10 minutes, the melt viscosity is low, and consequently it does notdisplay the drop preventing effect of the molten material, which ischaracteristic due to tetrafluoroethylene. In this regard, a V0 grade offlame retardancy according to the UL specifications cannot be obtained.

[0009] With respect to the stereo-specificity of the polypropylene resinused in the present invention, it can be of any polypropylene withoutspecific limitations as long as it is crystalline. In particular, acrystalline polypropylene resin can be used, wherein its isotacticpentad ratio measured with ¹³C-NMR (Nuclear Magnetic Resonance Spectrum)is 0.80˜0.99, or preferably 0.9˜0.99. In particular, a crystallinepolypropylene resin of 0.9˜0.99 of isotactic pentad ratio can bepreferably used.

[0010] With respect to the flame retardant polypropylene resincomposition of the present invention, at least one of flame retardantsis selected from the group of inorganic compounds such as magnesiumhydroxide, hydrotalcite, and ammonium polyphosphate, etc.; and the groupof halogenated compounds such as decabromodiphenylether, ethylene-bis(tetrabromophthalimide), bispentabromophenoxyethane, tetrabromobisphenyl A-bis(2,3-dibromopropylether), bis{(3,5-dibromo-4-(2′,3′-dibromopropyloxy))phenyl)}sulfone, etc. For thepurpose of achieving the effect of flame retardancy, the amount of flameretardants is preferably 10˜30 wt % of the composition.

[0011] With respect to the polypropylene resin composition of thepresent invention, commonly-used flame retardant aids may be used, orpreferably antimony oxide can be used. For example, antimony trioxide,or antimony pentoxide or the mixture thereof can be used. For thepurpose of achieving the effect of flame retardancy, the amount of theflame retardant aid is preferably 5˜10 of the composition.

[0012] With respect to the flame retardant polypropylene resincomposition of the present invention, an appropriate tetrafluoroethylenepolymer is a polymer containing 65˜76, or preferably 70˜76 wt %, offluorine. In addition to the homopolymers of tetrafluoroethylene, forthe same purpose as mentioned above, one can use a copolymer of othermonomers containing fluorine and tetrafluoroethylene, or a copolymer oftetrafluoroethylene and ethylenically unsaturated monomers, capable ofcopolymerization, without fluorine. The tetrafluoroethylene polymer maybe present to the extent of 0.10˜3 wt %, or preferably 1.5˜2 wt % of theresin composition of the present invention. Upon addition of thiscomponent therein, tetrafluoroethylene exists in the fibril form duringthe molding process of the resin composition consequently it has theeffect of preventing molten materials from dropping, at the time of theburning of the molded materials As for the tetrafluoroethylene polymerused in the present invention, it is preferable to use a polymer in theform of powder or solid. The method of producing a tetrafluoroethylenepolymer is well know as proposed for example in Houden-Wey, MetrodenderOrganischem Chmie, Volum 14/1 pg. 842-849 (Stuttgart 1961). The additionof a tetrafluoroethylene polymer in the composition according to thepresent invention reduces the amount of flame retardants necessarytherein and consequently it enhances the mechanical properties of theproducts produced from the composition of the present invention.Moreover, by adding a tetrafluoroethylene polymer, it prevents moldedbodies from burning during dripping of the combustible particles. Forobtaining the effect of flame retardancy therein, the amount of atetrafluoroethylene polymer is preferably 0.10˜3 wt %, and the amount offluorine contained in the tetrafluoroethylene polymer is preferably65˜76 wt %. If the amount of fluorine in tetrafluoroethylene polymer isless than 65 wt %, or more than 76 wt %, the effect of flame retardancyis not quite sufficient.

[0013] In addition to the above components, within the scope notdeviating the purposes of the present invention, conventional additivessuch as inorganic fillers and antioxidants can be added to the flameretardant polypropylene resin composition.

[0014] The present invention is described in detail by examples asfollows.

BEST MODE FOR CARRYING OUT THE INVENTION

[0015] The assessment for flame retardancy in the present invention wasbased on the vertical burning tests carried out along verticallyaccording to the “Tests for Flammability of Plastic Materials for Partsin Devices and Appliances” of UL Subject 94 (Underwriters Laboratories,Inc.). The thicknesses of the test section pieces used therein were{fraction (1/16)} and {fraction (1/32)} inch, respectively.

[0016] The compositions produced by the present invention wereclassified as UL94 V0 when they satisfied the following standards: A setof five test pieces with respective measurements of 127×12.7×1.6 mm wasplaced directly in contact with the flame (height of 19 mm). There weretwo contacts, respectively, which were maintained for ten seconds. Then,after ten or more seconds of flame burning, none of the test piecesshould burn. For applying the flame to the set of five test pieces forten times, the total duration of flame burning must not exceed 50seconds. None of the test pieces should drop flame particles. None ofthe test pieces should burn in flame to the point of the clamp's grip orburn further thereafter. After removing the test flame for the secondtime, none of the test pieces should undergo sustained burning for morethan 30 seconds.

[0017] To be classified as UL94 V1, the duration of flame burning pertest piece must not exceed more than 30 seconds. Moreover, with respectto applying the flame to the set of five test pieces for ten times, itrequires that the total duration of flame burning to be not longer than250 seconds. There, the burning must not sustain for more than 60seconds. Other standards are the same as the conditions as mentionedabove.

[0018] Those test pieces dropping flame particles while satisfying theother standards for classifying them to UV94 V1 were classified as UL94V2.

EXAMPLE 1

[0019] 6.6 kg of crystalline polypropylene homopolymer (as apolypropylene resin) having a melt flow rate (the melt flow amount ofmolten resin for 10 minutes at 230° C. with a 2.16 kg load) of 12 g/10minutes, 2.2 kg of decabromodiphenyl ether (S-102E produced byAlbermaler Corporation), 700 g of antimony trioxide (Sb203 produced byCheil Flame Retardant, Ltd. at 1.2 μm), 500 g of talc (KCN5200 producedby KOCH, Inc.), 40 g of polytetrafluoroethylene (7AJ produced by Dupont,Inc.), 10 g of calcium stearate, 10 g of antioxidant (1010 produced byCIBA-GEIGY, Inc.), and 20 g of IRGAFOS 168 (produced by CIBA GEIGY,Inc.) were added to a Hensel mixer and mixed therein for three minutes.By using a two-axis extruder with a diameter of 30 mm, the compositionas produced was molten and extruded into pellets at 190° C. The yieldedpellets were dried for three hours at 100° C. Then, they were molded byusing an injection-molding machine with the maximum temperature of acylinder fixed at 200° C. to provide test pieces for testing of flameretardancy. Then, the test pieces were tested for measuring flameretardancy, the results of which are shown in Table 1.

EXAMPLES 2˜4AND COMPARATIVE EXAMPLES 1˜3

[0020] Except for substituting the amount of a tetrafluoroethylenepolymer as an agent for improving the characteristic of a flaming dripin a composition with the amounts shown in Table 1, the pellets wereproduced under the same conditions as those mentioned in Example 1.Then, the yielded pellets were molded by using an injection-moldingmachine to provide the test pieces, and the test pieces were tested formeasuring flame retardancy, the results of which are shown in Table 1.

[0021] With respect to the flame retardancy of the resin compositions ofExamples 1˜4and Comparative Examples 1˜3, as shown in Table 1, when atetrafluoroethylene polymer was added as an agent for improving thecharacteristic of a flaming drip, the shape maintenance of the moltenmaterials was excellent. Moreover, the molten materials droppingthereto, which may cause ignition at the cotton wool laid 3 cm below thetest piece, were non-existence during burning. In short, they showedflame retardancy of UL V0. However, when the amount of atetrafluoroethylene polymer in the composition was 5 wt % or more, therewere no further effects on the characteristics of a flaming drip.

EXAMPLE 5

[0022] 6.6 kg of crystalline polypropylene homopolymer (as apolypropylene resin) having a melt flow rate (the melt flow amount ofmolten resin for 10 minutes at 230° C. with a 2.16 kg load) of 12 g/10minutes, 2.2 kg of decabromodiphenyl ether (S-102E produced byAlbermaler Corporation), 700 g of antimony trioxide (Sb203 produced byCheil Flame Retardant, Ltd. at 1.2 μm), 300 g of talc (KCN5200 producedby KOCH, Inc.), 40 g of polytetrafluoroethylene (7AJ produced by Dupont,Inc.), 10 g of calcium stearate, 10 g of antioxidant (1010 produced byCIBA-GEIGY, Inc.), and 20 g of IRGAFOS 168 (produced by CIBA GEIGY,Inc.) were added to a Hensel mixer and mixed therein for three minutes.By using a two-axis extruder with a diameter of 30 mm, the compositionas produced was melted and extruded into pellets at 190° C. The yieldedpellets were dried for three hours at 100° C. Then, they were molded byusing an injection-molding machine with the maximum temperature of acylinder fixed at 200° C. to provide test pieces for testing of flameretardancy. Then, the test pieces were tested for measuring flameretardancy, the results of which are shown in Table 1.

EXAMPLES 6˜8 AND COMPARATIVE EXAMPLES 4˜6

[0023] Except for substituting the amount of talc as an inorganic fillerand the amount of tetrafluoroethylene polymer in a composition with theamounts shown in Table 1, the pellets were produced under the sameconditions as those mentioned in Example 5. Then, the yielded pelletswere molded by using an injection-molding machine to provide the testpieces, and the test pieces were tested for measuring flame retardancy,the results of which are shown in Table 1.

[0024] As shown in Table 1, with respect to the flame retardancy of theresin compositions of Examples 5˜8 and Comparative Examples 4˜6, incases of adding tetrafluoroethylene polymer as an agent for improvingthe characteristics of a flaming drip, the shape maintenance of moltenmaterials in such a state was possible even if the amount of talc as aninorganic filler was 3 wt % or lower. There were no molten materialsdropping during burning, which may cause ignition at the cotton woollaid 30 cm below the test piece. In short, the flame retardancy of UL94V0 were achieved in these cases. In cases of not addingtetrafluoroethylene polymer, if the amount of talc in the compositionwas 20 wt % or less, the flame retardancy of UL94 V0 could not beobtained due to ignition by way of a flaming drip during burning.

EXAMPLE 9

[0025] 6.3 kg of crystalline polypropylene homopolymer (as apolypropylene resin) having a melt flow rate (the melt flow amount ofmolten resin for 10 minutes at 230° C. with a 2.16 kg load) of 12 g/10minutes, 2.4 kg of decabromodiphenyl ether (S-102E produced byAlbermaler Corporation), 800 g of antimony trioxide (Sb203 produced byCheil Flame Retardant, Ltd. at 1.2 μm), 500 g of talc (KCN5200 producedby KOCH, Inc.), 40 g of polytetrafluoroethylene (7AJ produced by Dupont,Inc.), 10 g of calcium stearate, 10 g of antioxidant (1010 produced byCIBA-GEIGY, Inc.), and 20 g of IRGAFOS 168 (produced by CIBA GEIGY,Inc.) were added to a Hensel mixer and mixed therein for three minutes.By using a two-axis extruder with a diameter of 30 mm, the compositionas produced was molten and extruded into pellets at 190° C. The yieldedpellets were dried for three hours at 100° C. Then, they were molded byusing an injection-molding machine with the maximum temperature of acylinder fixed at 200° C. to provide the test pieces for testing offlame retardancy. Then, the test pieces were tested for measuring flameretardancy, the results of which are shown in Table 1.

EXAMPLES 10˜14 AND COMPARATIVE EXAMPLES 7˜16

[0026] Except for substituting the amounts and the types of flameretardants, flame retardant aids, and talc in a composition with thoseshown in Table 1, the pellets were produced under the same conditions asthose mentioned in Example 9. Then, the yielded pellets were molded byusing an injection-molding machine, and the test pieces were producedfor measuring flame retardancy, the results of which are shown in Table1.

[0027] As shown in Table 1, with respect to the flame retardancy of theresin compositions of Examples 9˜14 and Comparative Examples 7˜16, incases of adding tetrafluoroethylene polymer as an agent for improvingthe characteristics of a flaming drip, the shape maintenance of moltenmaterials, irrespective of the types of flame retardants, was excellentwith respect to the flame retardancy tests. There were no moltenmaterials dropping during burning, which may cause ignition at thecotton wool laid 30 cm below the test piece. In short, the flameretardancy of UL94 V0 were achieved in these cases.

EXAMPLE 15

[0028] 6.8 kg of crystalline polypropylene homopolymer (as apolypropylene resin) having a melt flow rate (the melt flow amount ofmolten resin for 10 minutes at 230° C. with a 2.16 kg load) of 1.5 g(10minutes, 2.2 kg of decabromodiphenyl ether (S-102E produced byAlbermaler Corporation), 700 g of antimony trioxide (Sb203 produced byCheil Flame Retardant, Ltd. at 1.2 μm), 500 g of talc (KCN5200 producedby KOCH, Inc.), 40 g of polytetrafluoroethylene (7AJ produced by Dupont,Inc.), 10 g of calcium stearate, 10 g of antioxidant (1010 produced byCIBA-GEIGY, Inc.), and 20 g of IRGAFOS 168 (produced by CIBA GEIGY,Inc.) were added to a Hensel mixer and mixed therein for three minutes.By using a two-axis extruder with a diameter of 30 mm, the compositionas produced was molten and extruded into pellets at 190° C. The yieldedpellets were dried for three hours at 100° C. Then, they were molded byusing an injection-molding machine with the maximum temperature of acylinder fixed at 200° C. to provide the test pieces for testing offlame retardancy. Then, the test pieces were tested for measuring flameretardancy, the results of which are shown in Table 2.

EXAMPLES 16˜17 AND COMPARATIVE EXAMPLES 17˜18

[0029] Except for substituting the polyethylene resins with those withthe melt flow rates as shown in Table 2, the pellets were produced underthe same conditions as those mentioned in Example 15. Then, the yieldedpellets were molded by using an injection-molding machine, and the testpieces were tested for measuring flame retardancy, the results of whichare shown in Table 2.

[0030] As shown in Table 2, with respect to the flame retardancy of theresin compositions of Examples 15˜17 and Comparative Examples 17˜18,even with the polyethylene resins with the melt flow rates in the broadrange of 1.5˜40 g/10 minutes, the characteristics of a flaming dripcould be enhanced However, if it was 0.5 g/10 minutes or lower, theextrusion load at the time of the secondary processing was very high,with ensuing difficulties in even dispersion of flame retardants. Inthis regard, the flame retardancy of UL94 V0 could not be obtained inthese cases. Moreover, if the melt flow rate was 60 g/10 minutes ormore, the melting point of the substrate resin became too low in itself,and consequently it could not suppress the production of combustiblemolten materials dropping thereto. In short, it led to difficulties inobtaining flame retardancy of UL94 V0 TABLE 1 Assessment Composition1/16″ 1/32″ (B) Flame Flame Type (A)-1 (B)-1 (B)-2 (B)-3 (B)-4 (B)-5 (C)(D) (E) Drip Retardancy Drip Retardancy E1 66 22 — — — — 7 5 0.40 ND V0ND V0 E2 66 22 — — — — 7 5 0.10 ND V0 ND V0 E3 66 22 — — — — 7 5 2.00 NDV0 ND V0 E4 66 22 — — — — 7 5 3.00 ND V0 ND V0 CE1 66 22 — — — — 7 50.00 DB V2 DB V2 CE2 66 22 — — — — 7 5 0.05 DB V2 DB V2 CE3 66 22 — — —— 7 5 5.00 ND V1 ND V1 E5 68 22 — — — — 7 3 0.40 ND V0 ND V0 E6 66 22 —— — — 7 5 0.40 ND V0 ND V0 E7 61 22 — — — — 7 10 0.40 ND V0 ND V0 E8 5122 — — — — 7 20 0.40 ND V0 ND V0 CE4 61 22 — — — — 7 10 0.00 DB V2 DB V2CE5 51 22 — — — — 7 20 0.00 DB V2 DB V2 CE6 41 22 — — — — 7 30 0.00 D V0ND V0 E9 63 24 — — — — 8 5 0.40 ND V0 ND V0 E10 59 27 — — — — 9 5 0.40ND V0 ND V0 E11 64 — 24 — — — 7 5 0.40 ND V0 ND V0 E12 62 — — 25 — — 8 50.40 ND V0 ND V0 E13 82 — — — 12 — 6 — 0.40 D V0 D V0 E14 82 — — — — 126 — 0.40 D V0 D V0 CE7 63 24 — — — — 8 5 0.00 DB V2 DB V2 CE8 59 27 — —— — 9 5 0.00 D V2 D V2 CE9 63 — 24 — — — 8 5 0.00 DB V2 DB V2 CE10 59 —27 — — — 9 5 0.00 D V0 DB V2 CE11 62 — — 25 — — 8 5 0.00 DB V2 DB V2CE12 50 — — 27 — — 8 15 0.00 D V0 DB V2 CE13 82 — — — 12 — 6 — 0.00 DBV2 DB V2 CE14 79 — — — 14 — 7 — 0.00 DB V2 D V0 CE15 82 — — — — 12 6 —0.00 DB V2 DB V2 CE16 79 — — — — 14 7 — 0.00 DB V2 D V0

[0031] TABLE 2 (UNIT: 100 g) 1/16″ 1/32″ Flame Flame Type (A)-2 (A)-3(A)-4 (A)-5 (A)-6 (B)-1 (C) (D) (E) Drip Retardancy Drip Retardancy E1568 — — — — 22 7 5 0.40 ND V0 ND V0 E16 — 68 — — — 22 7 5 0.40 ND V0 NDV0 E17 — — 68 — — 22 7 5 0.40 ND V0 ND V0 CE17 — — — 68 — 22 7 5 0.40 DBV2 DB V2 CE18 — — — — 68 22 7 5 0.40 ND V1 ND V1

[0032] As shown above, as compared to the conventional flame retardantpolypropylene resin compositions, the flame retardant polypropyleneresin composition produced according to the present invention displaysflame retardancy of UL94 V0 by way of reducing the amount of flameretardants necessary for flame retardancy of UL94 V0 and consequentlyenhancing the mechanical properties of the products produced from thecomposition of the present invention. Moreover, irrespective of thetypes of flame retardants, the shape maintenance of the molten materialsin the flame retardancy test is excellent, without the molten materialsdropping during burning, which in turn may cause ignition at the cottonwool laid 30cm below the test piece.

What is claimed is:
 1. A flame retardant polypropylene resin compositioncomprising a polypropylene resin having a melt flow rate of 1.5˜40 g/10minutes at 230° C. with a 2.16 kg load; 10˜30 wt % of flame retardants,5˜10 wt % of a flame retardant aid; and 0.10˜3 wt % of atetrafluoroethylene polymer.
 2. The flame retardant polypropylene resincomposition according to claim 1, wherein said polypropylene resin is apolypropylene homopolymer, or a copolymer of propylene and α-olefin. 3.The flame retardant polypropylene resin composition according to claim1, wherein said flame retardants are one or more selected from the groupconsisting of inorganic compounds such as magnesium hydroxide,hydrotalcite, and ammonium polyphosphate, and halogenated compounds suchas decabromodiphenylether, ethylene-bis(tetrabromophthalimide),bispentabromophenoxyethane, tetrabromobisphenolA-bis(2,3-dibromopropylether), andbis((3,5-dibromo-4-(2′,3′-dibromoprophyloxy))phenyl)sulfone.
 4. Theflame retardant polypropylene resin composition according to claim 1,wherein said flame retardant aid is antimony trioxide, antimonypentoxide. or the mixture thereof.
 5. The flame retardant polypropyleneresin composition according to claim 1, wherein said tetrafluoroethylenepolymer is a polymer having 65˜76 wt % of fluorine